Three dimensionally fiber-reinforced composite riser and methods of making the same

ABSTRACT

The present invention relates to a three dimensionally fiber-reinforced riser and to the unitary or single-step methods of making the same. In one embodiment (a cross bow riser for example), the riser has an interior support with opposed side members and a front brace. The front brace has a depression centrally located therein. Two side ribs are also provided for structural support. Two pockets each optionally having a divider wall defining a top and bottom section are provided for receiving respective top and bottom pieces of a split limb, when a split limb is used. The riser can be made of a composite material having fibers aligned there within in the directions of the highest stresses for enhancing the structural strength of the riser. Other bow parts or components can likewise be made via composite material as well.

This U.S. utility patent application claims priority on and the benefitof provisional application 61/389,968 filed Oct. 5, 2010, the entirecontents of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an object such as a riser and inparticular to a three dimensionally fiber-reinforced riser and to themethods of making the same.

2. Description of the Related Art

It is a common product design goal to improve or replace conventionalitems with items having improved characteristics, such as improvementsin strength, rigidity and durability, material qualities and economicconcerns.

One industry where such enhancements are being made is in the archeryindustry. Archery risers, or simply risers, in the most basic formprovide support for archery limbs. The risers can also supportaccessories such as but not limited to arrow rests, sight components,quivers, wrist straps, cable sliding bars, string stops and otheraccessories. The limbs bend symmetrically about opposite ends of theriser during the first of two stages of use, namely the draw stage, tostore energy which, in turn, can be released during the second stage ofuse, namely the power stroke, to cause an arrow to be shot or projectedfrom the bow. Stresses of varying magnitudes and orientations developwithin the riser during use. Stresses can also develop within the riserduring the manufacturing process.

One examples of a background patent is U.S. Pat. No. 7,258,113 to Pilpelet al. and titled Thermoplastic Composite Bow Riser, Limb and Camillustrates a riser for an archery bow that is formed from a fibrouscomposite material, the matrix of which may be a high heat distortionthermoplastic polymer, a very high heat distortion thermoplasticpolymer, or a combination thereof. The riser may incorporate a spineformed from a different polymer or composite than the rest of the riser,or from metal. A method for producing a riser for an archery bowincludes the steps of introducing a polymeric composite into a mold froma first end of the mold to facilitate a particular orientation ofcomponents of the polymeric composite, molding the polymeric compositeto produce a billet that approximates a net shape of the riser, and thenmachining the billet to the final shape of the riser. While the subjectof this invention may work well for its intended purposes, its designand methods of manufacture can be improved upon.

Nothing is taught, shown or suggested in this patent as to how parts maybe consolidated via a unitary molded composite component.

This patent requires the use of a spine made of a different material toachieve a desired structural integrity. The use of a spine can lead todelamination of the thermoplastic, as there exists mismatched physicaland thermal properties between the spine and the remainder of the riser.The potential for delamination is enhanced due to the high stressconditions present during operation of the bow.

This patent also teaches the manufacture of a two dimensional product orlaminate. One disadvantage of having a laminate flat part structure isthat the fibers are only positioned in the two dimensions within theplane of the material, and ignores placement and orientation of fibersin the third geometrical dimension (i.e. in the direction of thethickness of the two dimensional laminate structure). In this regard, atwo dimensional product of this type may only be useful in plane-stressstate conditions.

This patent further teaches that the riser is machined to achieve theriser final shape and form. This requirement leads potentially to a hostof deficiencies.

For example, the machined product may be subject to exposed fiber ends.Any fibers having exposed ends are subject to increased risks ofpullout. The pullouts create voids in the product, and also can resultin areas of decreased localized material strength. Crack propagation canalso be a problem in areas of fiber pullout.

Still further, exposed fibers that remain intact can be subject to rapidoxidation and degradation, and there exists a possibility of separationbetween the fibers and resin.

It is particularly problematic that the locations which are mostsusceptible to these fiber problems are the areas where the materialrequirements are most demanding, namely, in the regions of the riserhaving three dimensional structures and where fine details or rapidchanges in dimension are present. Examples of these regions includecorners, generally curved surfaces and areas of radius.

Still further yet, the machined product can form relatively highfriction surfaces, or even worse, be subject to varying degrees offriction along the surfaces. This situation is quite problematic for aproduct such as a bow riser, as arrows typically come into contact withthe riser during launch and the changes in friction can alter thetrajectory and/or speed of the arrow.

Thus, there exists a need for a three dimensionally fiber-reinforcedcomposite riser and methods of making the same that solves these andother problems.

SUMMARY OF THE INVENTION

The present invention relates to three dimensionally fiber-reinforcedriser and to the unitary or single-step methods of making the same. Inone embodiment (a cross bow riser for example), the riser has aninterior support with opposed side members and a front brace. The frontbrace has a depression centrally located therein. Two side ribs are alsoprovided for structural support. Two pockets each optionally having adivider wall defining a top and bottom section are provided forreceiving respective top and bottom pieces of a split limb, when a splitlimb is used. The riser can be made of a composite material havingfibers aligned there within in the directions of the highest stressesfor enhancing the structural strength of the riser. Other bow parts orcomponents can likewise be made via composite material as well.

According to one advantage of the present invention, the riser can beformed from a single unitary piece of composite material therebyreducing the number of manufacturing steps and the numbers of partsproduced. For example, mounting features for sights, quivers,specialized grips, limb attachments, spring brakes and the like can beincorporated into the present invention without the need for secondarymanufacturing operations. Several components can be consolidated via thepresent invention leading to structural and economic advantages.Accordingly, the economic considerations of manufacture are enhanced bythe method of the present invention.

According to another advantage of the present invention, the riser ismade of a composite material without the need for a spine or otherstructural enhancing component. To the contrary, the required materialproperties are provided as a result of the design and manufacturing ofthe riser of the present invention.

Related, given that the riser is formed as a unitary piece, the risks ofdelamination are eliminated.

According to another advantage of the present invention, the fibers areadvantageously positioned and oriented in all three dimensions and therespective surfaces. The riser is designed to absorb the stressesapplied to it, both during use and manufacturing. In this regard, fiberscan wrap into the intricate and/or curvaceous portions of the riser,where structural demands may be the greatest.

According to a further advantage of the present invention, the riser isformed in a single molding process instead of being machined. Thisadvantageously provides many advantages including the elimination offiber pullouts and exposed fibers, both of which can lead to prematurefailure. To the contrary, the structural integrity of the presentinvention is enhanced during the manufacturing process as the fibersremains intact. Preselected orientation and quantity of fibers thatremain intact advantageously lead to products meeting desired structuralgoals.

Related, residual stresses caused during a traditional machining processare eliminated in the present invention, as the machining process itselfis eliminated in the preferred method of making the present invention.

According to a further advantage of the present invention, the surfacesof the riser may be uniform and smooth (or have any desired surfacecharacteristics), and may be a relatively low friction surface. Thisallows an arrow to behave in a predictable and favorable manner atlaunch.

Other advantages, benefits, and features of the present invention willbecome apparent to those skilled in the art upon reading the detaileddescription of the invention and studying the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one preferred embodiment of a limb andriser assembly of the present invention.

FIG. 2 is a front view of the limb and riser assembly illustrated inFIG. 1.

FIG. 3 is a top view of the limb and riser assembly illustrated in FIG.1.

FIG. 4 is an isolation perspective view of a preferred embodiment of theriser of the present invention.

FIG. 5 is a front view of the riser illustrated in FIG. 4

FIG. 6 is a side view of the riser illustrated in FIG. 4.

FIG. 7 is a schematic view showing the fiber orientation within theriser illustrated in FIG. 4.

FIG. 8 is a perspective view of an alternative riser embodiment of thepresent invention.

FIG. 9 is a front view of the alternative riser shown in FIG. 8.

FIG. 10 is a side view of the alternative riser shown in FIG. 8.

FIG. 11 is a perspective view of the alternative embodiment shown inFIG. 8 showing a preferred gate location and fiber orientation.

FIG. 12 is a reverse perspective view of the alternative embodimentshown in FIG. 8 showing a preferred gate location and fiber orientation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the invention will be described in connection with severalpreferred embodiments, it will be understood that it is not intended tolimit the invention to those embodiments. On the contrary, it isintended to cover all alternatives, modifications and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims.

Turning now to FIGS. 1-6, it is seen that an embodiment of a riser andlimb assembly is illustrated.

The riser 10 has opposed ends 11 and 12, a front 13 and a back 14, a top15 and a bottom 16. It is preferred that the riser 10 is formed as asingle integral component in a molding process. The riser 10 ispreferably symmetric about a central axis 17.

The riser 10 is made of a unitary piece forming the body 18. Body 18 hasan exterior surface 19 having predetermined surface characteristics. Inthe preferred embodiment, the surface 19 is relatively smooth. It isunderstood that different portions of the surface 19 can have differentsurface characteristics without departing from the broad aspects of thepresent invention. The surface 19 is unconstrained or independent of thequantity and distribution of the embedded fibers. The body has severalintricate portions, and the surfaces and interior volumes of each of theintricate portions are wrapped and/or filled with fibers in apreselected orientation and quantity. Also, it is understood that undermolding pressures, it is possible that a thin layer of resin can bepassed to the surface to further reduce or eliminate the effect ofembedded fibers on the surface ornamentation or characteristics.

Turning now to specific geometries of a first preferred embodiment,there is an interior support 20 having side members 21 and 22, and afront brace 23 is shown. The front brace 23 has a centrally aligneddepression 24 therein. Front brace 23 provides a place for a user's footto brace the bow during the cocking of the bow. The depression 24provides clearance for the shot arrow, or bolt, to pass after the shot.

A first side rib 30 is provided outside of side member 21. A second siderib 35 is provided outside of side member 22. The side ribs 30 and 35and the interior support 20 combine to form a robust structure. It isappreciated that relatively small ribs having minimized cross-sectionalareas are provided herein so as to minimize thermal gradients withresulting subsequent shrinkage and induced internal stresses from themanufacturing process. Also, it is noteworthy that ribs are designed sothat the flow of fibers and resin achieve the desired resultingorientations and quantity to provide the designed structural strength.

A pocket 40 is provided, and has a divider wall 41 defining a topsection 42 and a bottom section 43. An ear 44 is on the top of the topsection 42, and an ear 45 is on the bottom of the bottom section 43. Abolt hole 46 is formed through the divider wall 41.

A second pocket 50 is provided, and has a divider wall 51 defining a topsection 52 and a bottom section 53. An ear 54 is on the top of the topsection 52, and an ear 55 is on the bottom of the bottom section 53. Abolt hole 56 is formed through the divider wall 51.

It is appreciated that the pockets provide full control of the limbs,and also provide for proper limb spacing when split limbs are used. Itis further understood however, that singularly recessed pockets canalternatively be used when regular (or non-split limbs) are used withoutdeparting from the broad aspects of the present invention.

A connector 60 is at the back 14 of the riser for connecting to a stockof the crossbow.

A limb 80 can be connected to the riser 10 at pocket 40. The limb has atop piece 81 and a bottom piece 82 that nest in the top section 42 andbottom section 43, respectively, of pocket 40. A hub 83 is providedhaving a hole 84 there through to allow the limb 80 to be fastened tothe riser 10.

A second limb 90 can be connected to the riser 10 at pocket 50. The limbhas a top piece 91 and a bottom piece 92 that nest in the top section 52and bottom section 53, respectively, of pocket 50. A hub 93 is providedhaving a hole 94 there through to allow the limb 90 to be fastened tothe riser 10.

It is appreciated that while one preferred structure is illustrated,that other structures may be used without departing from the broadaspects of the present invention. It is also appreciated that whileother components of a crossbow, such as a stock, cams, triggers, triggerbox assemblies and/or stock rails are not specifically illustrated, thatthey nevertheless may be manufactured during the molding process of thepresent invention without departing from the broad aspects of thepresent invention.

During the design of the riser 10, the geometric size of a finishedriser is first determined based on structural and manufacturingrequirements. Next, stress orientation is determined through an analysissuch as finite element method analysis. This analysis determines themaximum stresses and orientation of those stresses and displacement thateach portion of the riser will be subject to during an external loadingcondition.

Knowing the maximum stresses that each portion of the riser will endureduring a loading condition, the flow of the liquid resin and fiber inthe mold are modeled using mold flow analytical techniques to achieve adesired fiber orientation within the molded part. FIG. 7 isrepresentative of a preferred fiber orientation and density of fiberplacement in the riser 10. Gate size and location, injection pressuresand mold temperatures are all chosen as they each have an effect on thefiber orientation. Given that the mold is a three dimensional cavity,the fibers will flow on all surfaces to achieve a desired fiberorientation.

It is a goal to maintain relatively small cross-sectional areas withinthe riser to prevent thermal imbalances and shrinkage, yet maintainsufficient size to allow for proper fiber flow and orientation.

Resins suitable for use in the present invention include engineeringpolymeric resins such as, but not in any way limited to, Nylons (PA) andtheir many compounds, polyurethanes (PU), PPS, PES, PEI, Epoxy andPolyesters. In this regard, any suitable resin may be used withoutdeparting from the broad aspects of the present invention.

Fibers for use with the present invention are preferably E-Glass,S-Glass, Aramid or Carbon. It is understood that other fibers may beused without departing from the broad aspects of the present invention.It is preferable that the fibers are long fibers having a length greaterthan 1 mm. It is even more preferred that the fiber length is greaterthan or equal to 3 mm. The fibers, as noted above, are distributedwithin the body in a three dimensional distribution pattern inpredetermined orientations and densities. In one production embodiment,the fibers have a starting length of approximately 15 to 25 mm. Thelengths are reduced during manufacturing due to attrition in the processand passage through orifices such as gates and runners.

It is understood that one preferred process as described herein isinjection molding. Yet, other processes, such as compression molding orcompression injection molding can be used without departing from thebroad aspects of the present invention.

It is preferred that injection temperatures are within the range of 280to 350 degrees Celsius. It is preferred that the mold temperature iswithin the range of 90 to 180 degrees Celsius.

Injection speeds of 50 to 70 mm/sec are preferred, as are injection backpressures of 25 to 50 psi.

These manufacturing parameters are preferred because they provide anenvironment suitable for a high degree of fiber length retention, yetallow for intended fiber distribution and orientation within the body.In this regard, it is readily understood that the fiber distribution andorientation can be variable within the volume of the body.

Turning now to FIGS. 8-12, it is seen that a preferred embodiment of analternative riser 110 is provided. The riser 110 has a first end 111, asecond end 112, a front 113, a back 114, a top 115 and a bottom 116.Riser 110 is a three dimensional unitary structure having a body 118with an external surface 119. Riser 110 is illustrative of a typicalcompound bow riser. It is appreciated that riser 110 can have anydesired shape without departing from the broad aspects of the presentinvention. Surface 119 can have any desired characteristics.

The riser 110 has a pocket 120 at the top 115 of the riser 110. Bolthole 121 is provided for connecting a limb (not shown) to the riser.

The riser 110 also has a pocket 130 at the bottom 116 of the riser 110.Bolt hole 131 is provided for connecting a limb (not shown) to theriser.

The body 118 of the riser 110 defines several riser features, includinga grip 140, sight mounts 150, cable rod mounts 160 and an arrow shelf170. It is appreciated that these and any other desired features can bemade in a single three dimensional unitary piece in a molding processsimilar to the process described above.

Looking now specifically at FIGS. 11 and 12, it is seen that preferredgate locations 180 and 180A, respectively, and the resulting fiberorientations are illustrated. Specifically, it is seen that fibers areoriented initially generally perpendicular to the gate locations andspread in line with the flow of the resin and fibers. The fiberorientations then follow the contours of the riser and hence wrap fullyabout intricate components of the riser as the fibers and resin flow tofill the mold cavity.

According to another aspect of the present invention, the risers 10 and110 can be designed for specific performances such as draw weightsand/or arrow speeds. For example, the risers can be designed and ratedfor specific draw weights including but not limited to 40-70 lbs. forcompound bows or 180 to 220 lbs. for cross-bows. Also, target arrowspeeds including but not limited to the range of 350-410 feet per secondcan be designed. It is understood that the stresses from these or otherloads can be determined wherein risers with requisite strength (due todimensions, fiber orientations and quantity) can be produced toeffectively withstand the stresses.

Thus it is apparent that there has been provided, in accordance with theinvention, a three dimensional composite riser and methods of making thesame that fully satisfies the objects, aims and advantages as set forthabove. While the invention has been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modifications, and variations as fallwithin the spirit and broad scope of the appended claims.

We claim:
 1. A riser comprising: a body of a three dimensional unitarystructure formed in a one step, automated industrial compositemanufacturing technique that is an injection molding process using amold and deriving full structural integrity internally without a spine,said body having a body top, a body bottom, a body front and a bodyback, and a body surface; said body further comprising a selected amountof fibers three dimensionally arranged in a preselected manner and in apreselected and variable density within said body as a result of a flowof said selected amount of fibers and a resin within the mold, saidresin having a liquid form and a solid form, wherein said selectedamount of fibers are a selected amount of flowable fibers when saidresin is in said liquid form, said selected amount of fibers being fullyembedded within said body thereby preventing an amount of fiber pulloutsand an amount of exposed fibers, and said selected amount of fibers havean orientation, said orientation of said selected amount of fiberswithin said body being constrained only by said resin when said resin isin said solid form; said body surface has a plurality of body surfacecharacteristics that are independent of said preselected manner and saidpreselected and variable density of said selected amount of fibers; andsaid body further comprising a plurality of pockets, said plurality ofpockets being adapted to receive a plurality of bow limbs, at least someof said selected amount of fibers being flowed to and wrapped aroundsaid plurality of pockets when said resin is in said liquid form.
 2. Theriser of claim 1 wherein said selected amount of fibers are long fibershaving a length greater than or equal to 1 mm.
 3. The riser of claim 2wherein said long fibers have a length greater than or equal to 3 mm andless than 25 mm.
 4. The riser of claim 1 wherein said selected amount offibers are selected from the group of: E-Glass; S-Glass; Aramid; andCarbon.
 5. The riser of claim 4 wherein said resin is selected from oneof the following: Nylon; Polyurethane; PPS; PES; PEI; Epoxy; andPolyester.
 6. The riser of claim 5 wherein said injection molding has aninjection temperature of between 280 to 350 degrees Celsius.
 7. Theriser of claim 5 wherein said injection molding has a mold temperatureof between 90 to 180 degrees Celsius.
 8. The riser of claim 5 whereinsaid injection molding comprises an injection speed of between 50 and 77mm/sec.
 9. The riser of claim 5 wherein said injection molding has aninjection back pressure of between 25 and 50 psi.
 10. The riser of claim1 wherein said body surface characteristics that are characteristics arevariable.
 11. The riser of claim 1 wherein said riser is one of a crossbow riser and compound bow riser.
 12. The riser of claim 1 wherein saidbody comprises intricate three dimensional portions, and said fiberswrap said intricate three dimensional portions.
 13. A riser made in amold and comprising: a body of a three dimensional unitary structureformed in an injection molding process and deriving full structuralintegrity internally without a spine, said body having a body top, abody bottom, a body front and a body back, and a body surface, said bodyfurther having a first pocket with a first pocket bolt hole forconnecting to a first limb and a second pocket with a second pocket bolthole for connecting to a second limb; said body further comprising aselected amount of fibers three dimensionally arranged in a preselectedmanner and in a preselected and variable density within said body, saidbody further being comprised of a resin having a solid form and a liquidform, said selected amount of fibers having a length greater than orequal to 3 mm, said selected amount of fibers further being embeddedwithin said body and which are not exposed exterior of said body and arewrapped around said first pocket bolt hole and said second pocket bolthole in a predetermined orientation and density as a result of saidresin and said selected amount of fibers flowing within the mold, saidselected amount of fibers are a selected amount of flowable fibers whensaid resin is in said liquid form and said selected amount of fibershave an orientation, said orientation of said selected amount of fiberswithin said body being constrained only by said resin when said resin isin said solid form; and said body surface has a plurality of bodysurface characteristics that are independent of said preselected mannerand said preselected and variable density of said selected amount offibers.